The proposed research aims at studying the development of phonetic perception, that is, the identification and discrimination of acoustic dimensions that differentiate the phonemes of a language. The research involves three related objectives: 1) description of the development of phonetic perception in normal children, 2) investigaton of the relationship between perceptual and articulatory development in normal children, and 3) exploration of possible perceptual deficits in children with articulation disorders. We will study the identification and discrimination of contrasts between /r/, /l/, /w/ and /y/ in initial, final, and intervocalic syllable position and in consonant cluster. Both synthetically generated and naturally-produced recorded stimulus materials will be used to test normally-developing children from two to five years of age. We will use the same materials and procedures to test children with articulation disorders requiring remedial treatment. In conjunction with perceptual testing we will do careful testing and analysis of articulation, using a distinctive features analysis approach. We will ask specific questions about the course of development of perception in relation to articulatory development, both for normal and articulation-disordered children. Our goals are to trace the course of normative development of speech perceptual skills and to describe the possible perceptual deficits in disordered children as they relate to their specific articulation problems. Finally, we will explore whether perceptual tests of disordered children are predictive of speech therapy success and whether perceptual training with synthetic materials is valuable in therapy programs with children who show perceptual deficits that are related to their articulation disorders.